Anaerobic adhesive systems are those which are stable in the presence of oxygen, but will polymerize in the absence of oxygen. Polymerization is initiated by the presence of a peroxy compound. The cured cross-linked resins serve as sealants and as adhesives.
Typical resin monomers are terminated with polymerizable acrylate esters such as methacrylate, ethacrylate and chloroacrylate esters. The other ingredients typically present are an initiator, preferably an organic hydroperoxide such as cumene hydroperoxide, tertiary butyl hydroperoxide and the like. There is also normally provided a stabilizer against free radical intiation such as a qunione or hydroquinone, in an amount sufficient to prevent premature polymerization of the adhesive due to decomposition of the peroxy compound. There are also preferably present one or more accelerators which are typically organonitrogen compounds such as tertiary amines, imides, sulfonamides and the like which promote the rate of cure.
Cure will be accelerated by the presence of a suitable metal, such as a transition metal, or its ion.
An anaerobic adhesive is applied to one or both of the surfaces to be joined. When the two surfaces are joined and oxygen excluded, cure will be initiated. As is well known, surfaces such as glass may require application of a suitable accelerator such as a transition metal compound, which will increase the rate of cure upon the substantial exclusion of oxygen or air.
Anaerobic adhesives have been well published in the art as for instance, in U.S. Pat. Nos. 2,895,950; 3,041,322; 3,043,820; 3,046,262; 3,203,941; 3,218,305; 3,300,547; 3,435,012; 3,547,851 and 3,625,875.
Anaerobic adhesive systems are typically supplied from a water-like liquid to a light-weight grease in consistency. One end-use application is to apply the adhesive to the threads of a bolt or mating nut which are then assembled. The adhesive fills the spaces between the threads which excludes oxygen and enables cure. In the normal situation, the metals present in the bolt or the nut accelerate cure.
A problem exists, however, in fixturing other surfaces together with initiation and completion of cure, and in providing a controlled quantity of anaerobic monomer to the surfaces to be bonded.